'\" et
.TH FG "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
fg
\(em run jobs in the foreground
.SH SYNOPSIS
.LP
.nf
fg \fB[\fIjob_id\fB]\fR
.fi
.SH DESCRIPTION
If job control is enabled (see the description of
.IR set
.BR \-m ),
the
.IR fg
utility shall move a background job from the current environment (see
.IR "Section 2.12" ", " "Shell Execution Environment")
into the foreground.
.P
Using
.IR fg
to place a job into the foreground shall remove its process ID from the
list of those ``known in the current shell execution environment''; see
.IR "Section 2.9.3.1" ", " "Examples".
.SH OPTIONS
None.
.SH OPERANDS
The following operand shall be supported:
.IP "\fIjob_id\fR" 10
Specify the job to be run as a foreground job. If no
.IR job_id
operand is given, the
.IR job_id
for the job that was most recently suspended, placed in the background,
or run as a background job shall be used. The format of
.IR job_id
is described in the Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 3.204" ", " "Job Control Job ID".
.SH STDIN
Not used.
.SH "INPUT FILES"
None.
.SH "ENVIRONMENT VARIABLES"
The following environment variables shall affect the execution of
.IR fg :
.IP "\fILANG\fP" 10
Provide a default value for the internationalization variables that are
unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 8.2" ", " "Internationalization Variables"
for the precedence of internationalization variables used to determine
the values of locale categories.)
.IP "\fILC_ALL\fP" 10
If set to a non-empty string value, override the values of all the
other internationalization variables.
.IP "\fILC_CTYPE\fP" 10
Determine the locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as opposed to
multi-byte characters in arguments).
.IP "\fILC_MESSAGES\fP" 10
.br
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard error.
.IP "\fINLSPATH\fP" 10
Determine the location of message catalogs for the processing of
.IR LC_MESSAGES .
.SH "ASYNCHRONOUS EVENTS"
Default.
.SH STDOUT
The
.IR fg
utility shall write the command line of the job to standard output
in the following format:
.sp
.RS 4
.nf

"%s\en", <\fIcommand\fR>
.fi
.P
.RE
.SH STDERR
The standard error shall be used only for diagnostic messages.
.SH "OUTPUT FILES"
None.
.SH "EXTENDED DESCRIPTION"
None.
.SH "EXIT STATUS"
The following exit values shall be returned:
.IP "\00" 6
Successful completion.
.IP >0 6
An error occurred.
.SH "CONSEQUENCES OF ERRORS"
If job control is disabled, the
.IR fg
utility shall exit with an error and no job shall be placed in the
foreground.
.LP
.IR "The following sections are informative."
.SH "APPLICATION USAGE"
The
.IR fg
utility does not work as expected when it is operating in its own
utility execution environment because that environment has no
applicable jobs to manipulate. See the APPLICATION USAGE section for
.IR "\fIbg\fR\^".
For this reason,
.IR fg
is generally implemented as a shell regular built-in.
.SH EXAMPLES
None.
.SH RATIONALE
The extensions to the shell specified in this volume of POSIX.1\(hy2017 have mostly been based
on features provided by the KornShell. The job control features
provided by
.IR bg ,
.IR fg ,
and
.IR jobs
are also based on the KornShell. The standard developers examined the
characteristics of the C shell versions of these utilities and found
that differences exist. Despite widespread use of the C shell, the
KornShell versions were selected for this volume of POSIX.1\(hy2017 to maintain a degree of
uniformity with the rest of the KornShell features selected (such as
the very popular command line editing features).
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "Section 2.9.3.1" ", " "Examples",
.IR "Section 2.12" ", " "Shell Execution Environment",
.IR "\fIbg\fR\^",
.IR "\fIkill\fR\^",
.IR "\fIjobs\fR\^",
.IR "\fIwait\fR\^"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 3.204" ", " "Job Control Job ID",
.IR "Chapter 8" ", " "Environment Variables"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
